Scientific & Technical Report
FCASRCSENa
Separations Technologies to Improve
Amine System Reliability: A Case Study
Co-Authors:
Anabel Raymond, Marsulex Inc.
Francois Levesque, Pall Canada Ltd.
Hanif Lakhani, Pall Canada Ltd.
Paper originally presented at the Laurance Reid Gas Conditioning Conference, Norman, OK,
February 2008
Abstract
Today, many refineries are finding their amine
systems are struggling to handle the increased
acid gas loads resulting from low sulphur
gasoline and diesel production. As initiatives
to increase amine and sulphur plant reliability
are undertaken, it is critical that suitable
filtration and separation technology is
employed to remove particulate and liquid
contaminants from entering the amine circuits.
Marsulex Montréal Inc. operates a sulphur
handling facility located adjacent to two
refineries in Montréal. Hydrogen sulphide-rich
amine is sent by pipeline to the Marsulex plant
where the amine is regenerated and returned
to the two refineries. As part of a 50%
expansion project that was completed in 2006,
Marsulex Montréal Inc. chose to install the
latest separations technology to reach the
maximum design capacity by eliminating the
par ticulate
and
hydrocarbon
ingression/contamination issues that were
previously reducing plant reliability due to
fouling. The deployment of rich-side filtration
and high-performance liquid/liquid coalescers
mitigated expensive equipment replacement
and saved a significant capital expense.
1
Introduction:
Today, many refineries are finding their amine
systems are struggling to handle the increased
acid gas loads resulting from low sulphur
gasoline and diesel production. As initiatives
to increase amine and sulphur plant reliability
are undertaken, it is critical that suitable
filtration and separation technology is
employed to remove particulate and liquid
contaminants from entering the amine circuits.
Marsulex Montréal Inc. operates a sulphur
handling facility located adjacent to two
refineries in Montréal. The hydrogen sulphide
laden (rich) amine solution from the various
refinery contactors is gathered and transported
by pipeline to the Marsulex plant for
regeneration. Once regenerated, the lean amine
is returned to the two refineries’ mix of
contactors. The sulphur is extracted and
recovered by Marsulex. Marsulex’s sulphur
processing facility in Montréal is one of the
largest of its kind in the conventional crude
oil refining industry in Canada. This facility has
provided sulphur removal and compliance
services to refineries in the area for more than
40 years, and has never experienced an
unscheduled outage.
As part of a 50% expansion project that was
completed in 2006, Marsulex Montréal Inc.
chose to install the latest technology available to meet stringent requirements for
plant reliability and performance.
Amine Contamination:
With expansions to existing refineries, the
shift in crude diets to heavier and more sour
“opportunity crudes” refinery amine circuits
and sulphur plants are under more stress than
ever before. With these increased sulphur
loads, corrosion products, liquid hydrocarbons
and organic acids are making their way into
the amine units.
That amine cleanliness plays a crucial role in
overall amine and sulphur plant performance
and reliability is well known and documented.
Contaminants must be reduced or eliminated
to ensure reliable plant operation and
environmental compliance. Refiners (and gas
plants) have used different filtration and
separation methods to combat the most
common contaminants found in amine circuits
with mixed results. What is generally accepted
as good practice is that total suspended solids
in an amine circuit should be kept below 1
ppmw,1 and liquid hydrocarbons and organic
acids must be reduced to levels as close to zero
1
as possible.
* Particulate matter found in amine solutions
are, generally speaking, corrosion byproducts. Solid contaminants are known to
stabilise foams when foaming occurs. A
review of field test data from Pall’s databases
going back many years has shown a
consistent trend – that the particle size
distribution (PSD) of suspended solids is
generally finer than 20 µm, with the majority
of par ticles being found in the
sub-10 µm category. This observation has
been generally consistent even when total
suspended solids have varied from site to
site.
On the next page is a summary of amine
circuit filtration data compiled from Pall’s
Scientific and Laboratory Services (SLS) field
tests. The data is a composite of results
obtained in 10 countries, from 17 refineries
owned by 10 oil companies.
Verma, Narendra; Verma, Anil; 2009, “Amine System Problems Arising from Heat Stable Salts and Solutions to
Improve
Performance,” Fuel Processing Technology, Vol. 90, Issue 4.
Brown, Jr, Robert L., Hashemi, Reza; 1993, “Predicting Contamination Levels of Upset Conditions in Amine
2
Figure 1:
Composite of TSS
Results for Various
Amines
Amine Contamination
120
100
TSS
(ppmw)
Ucarsol
80
MEA
60
MDEA
Flexsorb
40
Selexol
20
DEA
0
Figure 1 above shows DEA as the most sampled
amine, and exhibiting the widest band of
contamination – ranging from a few ppmw to
nearly 120 ppmw. What is telling is that in
nearly all cases, the TSS levels exceed the
recommended best practice of no more than
1 ppmw suspended solids as advised in the
Figure 2 (left):
PSD for DEA
Samples
In the figures below, we see the PSD for several
samplings of DEA and MDEA (Figures 2 & 3)
showing that the majority of particles are
sub-20 µm in size.
MDEA Contamination - PSD
DEA Contamination - PSD
100
Percentage (number)
Percentage (number)
Figure 3 (right):
PSD for MDEA
Samples
expert literature.
80
60
40
20
0
0
20
40
60
80
100
Particles Size (micron)
In complex refineries, ingressing liquid
hydrocarbons can come from amine/LPG
contactors or as condensibles in the refinery
fuel gas. Typically, poor liquid/liquid contactor
outlet disengagement between LPG and amine
or inadequate inlet separation of free liquids
in refinery fuel gas entering vapour/liquid
contactors is the root cause. In complex
refineries where there are multiple contactors,
and when it is difficult to pin-point culprit
streams, the best option is to deploy central
filtration and separation as a means to
eliminate free liquid hydrocarbons from the
amine. High-performance liquid/liquid
coalescers (Pall’s PhaseSep® technology) can
break the stable, rich-amine/hydrocarbon
emulsion that can have adverse effects on the
amine unit and sulphur plant operations, which
can in turn impact overall refinery SO 2
emissions.
Within the amine circuit itself, the impact would
100
80
60
40
20
0
0
20
40
60
80
100
Particles Size (micron)
be felt in the rich/lean heat exchangers,
regenerator, re-boiler tubes, and tower trays
and packing, if left untreated. The consequences
can range from heat exchanger fouling,
hydrocarbon ingression in the sour-water reflux
discharge, increased corrosion, high amine
losses due to foaming in contactors, formation
of amine degradation products, and/or
generation of heat stable salts.
The efficiency of the sulphur recovery unit
and the converter catalyst life are also affected
by carried-over hydrocarbons in the acid gas.
In the event of a serious hydrocarbon carryover episode, the consequences can be much
more severe, including soot deposition in the
converters, runaway hydrocarbon combustion
in the Claus unit, and high SO2 emissions
resulting in regulatory penalties and possibly
expensive capacity reductions. In the worst
cases, there might be the necessity to switch
to sweeter crude slates as a mitigating strategy.
3
Rich-Side PhaseSep Liquid/Liquid Coalescer to Separate Hydrocarbons:
In the rich-amine side of the process, the
proposed system will perform a dual role as
follows:
• 100% Rich-Side Filtration - remove solid
particles - mainly FeS corrosion products
• Eliminate the free-hydrocarbon ingression
to the downstream process to near solubility
levels
Figure 4:
Full-Flow Rich-Side
Filter and
Liquid/Liquid
Coalescer System
Py-gas
Sump
Pre-conditioning
Filters
Outlet
Coalescers
Heavy Oil
Sump
The PhaseSep coalescer is a multiple-stage
system starting with pre-filtration (see Figure
4 below) that will remove particulate matter,
provide protection, and pre-condition the feed
to the coalescer. The coalescence stage that
follows breaks the emulsion and allows the
capture of dispersed hydrocarbon phase
droplets, resulting in the separation of the two
dissimilar streams. PhaseSep Liquid/Liquid
coalescers operate over a wide range of
conditions, including where:
• The emulsion has an IFT as low, or lower
than 5 dyne/cm (PhaseSep coalescers have
been applied in applications with an IFT as
low as 0.5 dyne/cm)
• The dispersed phase fluid is hydrocarbon,
Inlet
There are three essential steps to achieving an efficient liquid/liquid separation:
Stage 1: Pre-filtration
Stage 3: Separation
A rich-side full-flow pre-filter is essential to
protect and provide maximum operating life
to the liquid/liquid (L/L) coalescer. At the same
time, and more importantly, 100% rich-side
filtration prevents the passage of suspended
solids that may deposit in downstream
equipment such as rich/lean heat exchangers,
column packing or trays, and re-boilers.
The coalesced dispersed phase separates in the
settling zone of the coalescer housing. Due to
the density difference on the two phases, these
separated liquids exit through separate drain
and outlet connections at the back end of the
L/L coalescer housing.
Stage 2: Coalescence
The two-phase liquid emulsion enters the
coalescing element and flows inside-to-outside.
This is where small, suspended droplets of
the dissimilar fluid come together, or coalesce,
as the emulsion moves through the proprietary,
specially formulated coalescer medium.
4
The Marsulex Experience:
Up until 2004, the Marsulex amine unit was
relatively reliable. Although the unit never
had to be shut down for unplanned
maintenance, its efficiency and maintenance
costs were affected by amine contamination.
The residence time of the flash-drum was 22
minutes on average, with a design residence
time of 19 minutes. This was sufficient to
handle most hydrocarbon carr y-over
conditions. A simple particle filter assembly
was installed on a 15 - 20% kidney loop on
the lean amine side. It offered partial filtration
of the lean amine prior to the refiners’
contactors, but no protection for the Marsulex
amine unit and sulphur plant.
Following the planned 2006 expansion project,
the maximum amine recirculation flow capacity
would increase, and therefore, reduce the
residence time in the flash-drum. The
operational residence time would be reduced
to 13 minutes (at operating liquid level) or 9
minutes (at 50% liquid level). This was
considered insufficient to adequately separate
liquid hydrocarbon from the amine, raising
serious concerns about the reliability of the
plant under the new operating regime.
In preparation, Marsulex invited Pall to perform
an on-site demonstration of rich-side full-flow
pre-filtration and L/L coalescence. Testing
performed during the fall of 2004 helped better
define the level of contamination at the outlet
of the existing flash-drum. The site trials also
validated the effectiveness of rich-side filtration,
and confirmed the efficiency of the
liquid/liquid coalescer technology at separating
hydrocarbons from rich-amine.
During on-site testing, the following observations were made:
1. Even with adequate flash-drum residence
time, hydrocarbon/amine emulsion remained
stable, as evidenced by rich-amine samples
remaining hazy for longer than three weeks
(see Figure 5-B). Pall’s high-efficiency
PhaseSep liquid/liquid coalescer was capable
of breaking and separating this emulsion in
a single pass.
2. Rich-amine particulate concentrations vary
substantially depending on the refinery’s
operating conditions at a given point in
time. Using a 10µm absolute-rated filter
(Beta10 µm = 5000) helped reduce
Figure 5:
Test Samples
Rich Amine (DEA 25%):
Filtration and Liquid/Liquid Coalescer September 2004
INLET
(10 µm absolute)
OUTLET
(10 µm absolute)
OUTLET
(PhaseSep)
suspended solids to concentrations near or
below 1 ppmw.
3. Hydrocarbon (C5 to C60) levels found
upstream of the L/L coalescer pilot unit
ranged from 86 to 193 ppmw, and included
low levels of benzene, toluene, ethylbenzene, and xylene. Pall’s PhaseSep L/L
coalescer reduced overall hydrocarbon levels
to near solubility in amine, based on a total
extractable hydrocarbon analysis, utilizing
a Horuba Oil Content Analyzer (extractive
IR analyzer).
4. The average solids loading at the outlet of
the flash tank (inlet of the rich-side filter)
was
5 ppmw, with the lowest data point being
2 ppmw and the highest being 10 ppmw.
The average solids loading at the outlet of
A: Rich-amine sample at the outlet of the flash
tank. Note the solution color, indicative of
finely divided corrosion particles – FeS.
B: Rich-amine sample following 10 µm (Beta
5000) filtration. Note the haze – indicative of
a stable emulsion. This sample remained hazy
and unchanged for three weeks.
A
B
C
C: L/L coalescer outlet sample – clear and bright
after a single pass through the PhaseSep L/L
coalescer. Emulsion was broken and liquid
hydrocarbons separated.
5
Marsulex Solution:
Based on the field trial results, Marsulex made
the decision to install a full-flow, duplex
Figure 6:
Marsulex Amine
Unit Flow
Schematic
filtration package followed by a full-flow highperformance PhaseSep liquid/liquid coalescer
Cooling Water
E-230
Lean Amine
Tank
E-210
Light
H/C
Foul Amine
Return
Foul Amine
Flash Tank
Liquid
H/C
Amine
Regen.
Tower
E-211
E-212
E-213
E-214
E-215
E-221
E-222
E-223
E-224
Duplex Pre-filters
PhaseSep Coalescer
Steam
Figure 7 (left):
Duplex Ultipleat®
High Flow
Rich-Amine Filters
Figure 8 (right):
PhaseSep L/L
Coalescer Unit
Marsulex Operating Data:
The rich-side filter and coalescer units were
installed early in 2006 and started up in June
of that year. Prior to start-up of the equipment,
the rich-amine was hazy and had a green/gray
color at the outlet of the flash tank. Since the
unit has been in operation, amine samples at
the outlet of the filtration and coalescing system
are clear and bright, exhibiting the
characteristic light straw color of a clean amine,
just as was seen in Figure 5-C.
It was observed both in amine analysis and
overall process stability that the amine quality
has improved. The most significant
6
improvement has been in the consistently low
concentration of suspended solids. Prior to
the rich-side filtration coming on-line, the total
suspended solids in the circuit would reach 30
ppmw. Today, the solids are found to be in the
1 ppmw range on average, downstream of the
rich-side filter. With the L/L coalescer in place,
the continuous low-level hydrocarbon
ingression is being removed everyday. More
critically, when episodic hydrocarbon spikes
occur, the L/L coalescer responds immediately
by separating the liquid hydrocarbon slugs,
preventing circuit contamination and
Upset:
Since start-up of the rich-side filters and L/L
coalescers, there has only been one major
hydrocarbon carry-over to the Sulphur
Recovery Unit (SRU) and one major foaming
incident at the refinery contactors.
On the first occasion, an upset occurred at
the time when the filters and L/L coalescer
were by-passed for filter element change-out.
This was during a period of very high solids,
and filter life was short. The event should
have been a warning for the larger hydrocarbon
spike that followed. Following the five-hour
shutdown to replace the filter elements, it
Figure 9 (left):
Coalescer
Performance, 2007
Figure 10 (right):
Coalescer
Performance, 2008
took three days and eight filter replacements
to clean the particles and hydrocarbon out of
the amine loop and restore stability.
The second incident was most likely due to
hydrocarbon contamination of the amine
during a coalescer shutdown. However, given
the system is a closed loop, it cleaned up and
recovered once the coalescer was returned to
service. Employing the best practice of richside filtration and hydrocarbon coalescence
proved the system can, and will, recover
quickly. The alternative is unchecked
contamination of the circuit that conventional
separations techniques are inadequate at
Hydrocarbon Extracted by the Coalescer F-212 (US gal)
300
280
260
240
220
200
180
160
140
120
100
80
60
40
20
0
20-Nov-07
Total 2008 Hydrocarbon Extracted from F-212 (US gal)
800
5 hours Coalescer
shutdown
Total H/C extracted for JAN-JUN’07: 1449 US gal
Total H/C extracted for DEC’07:
1583 US gal
700
600
500
400
300
81 hours
Coalescer
shutdown
200
100
0
27-Nov-07
04-Dec-07
11-Dec-07
18-Dec-07
25-Dec-07
Since December 2007, the system has been
operating without any required coalescer
shutdown. In February 2009, there was another
major hydrocarbon carry-over from one of the
refineries. This time the coalescer extracted 840
US gallons (20 bbl) of hydrocarbon liquid over
a two-day period. High solids did not
accompany this event, and the filter did not
plug prematurely. With the separation train
remaining on-line, there was no impact on
the amine loop and the situation returned to
normal as soon as the hydrocarbon
contamination source was located and
addressed.
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
To date, the amine heat exchanger train, reboilers, and regenerator tower have been
performing without any need for shutdown.
Unfortunately, we cannot compare performance
before and after the installation of the rich-side
equipment because the entire circuit was
significantly modified during the 2006 project.
However, directionally, Marsulex can confirm
the general fouling tendency is greatly reduced
vs. prior to the filtration unit start-up.
Today, Marsulex is projecting a three-year or
better turn-around schedule for the entire heat
exchanger train. The re-boiler cleaning
schedule will be based on the trends revealed
from Marsulex’s monitoring program.
7
Process Benefits:
The most important benefit that the system
provides is an increase in overall reliability of
the amine system and sulphur plant. While
the system’s ability to allow for quick recovery
after a particulate and/or hydrocarbon
contamination event – which keeps the system
performing at capacity – is the primary benefit,
the operating costs are also greatly improved
due to longer time between cleaning, and
better hydrocarbon recovery.
The lean/rich exchangers cleaning frequency
has returned to a PM (preventative
maintenance) schedule, five in three years vs.
a required eight in three years due to
significant fouling of the heat exchanger train.
Over time, Marsulex will re-assess the schedule
based on inspections. The frequency reduction
is expected to save a minimum of $100,000 on
maintenance costs. This is in addition to the
energy savings realized with reduced steam
consumption in the regenerator re-boiler (not
calculated here).
The liquid/liquid coalescer allowed greater
liquid hydrocarbon recovery when compared
to the flash-drum alone. On average, the
amount of liquid hydrocarbon recovered is
increased by 25%. For example, in 2008, this
resulted in the recovery of an additional 4,830
US
gallons
(115 bbl) of liquid hydrocarbon. This offsets
fuel costs since the recovered oil is now being
fed to a boiler. Most importantly, the removal
of this volume of hydrocarbon ensures amine
circuit stability, and protection of the
Conclusion:
Rich-amine filtration and liquid/liquid
coalescence is crucial for the removal of
particulate matter such as corrosion products
and liquid hydrocarbons circulating in the
amine loop immediately downstream of the
flash-drum. As demonstrated at Marsulex, the
best practice targets of ~1 ppmw (avg.)
suspended solids, and free liquid hydrocarbon
levels at near solubility, are achievable.
High performance liquid/liquid coalescers
provide a more efficient and economical means
for the removal of liquid hydrocarbons from
an amine stream when compared to carbon
beds or centrifugal devices. Liquid/liquid
coalescers are also a highly efficient means to
control incoming hydrocarbon slugs and
maintain amine loop stability after an event.
8
The filtration and separation train provides
protection of the lean/rich heat exchangers,
regenerator tower, and reboilers and lean
amine coolers. The benefits are: reduction in
overall energy consumption, acid gas mass
transfer maximisation, prevention of foaming
episodes and loss of amine, maintaining the
re-boiler tubes in good condition, which
prevents fouling and formation of local ‘hotspots’ responsible for amine degradation, and
the initiation of the problematic corrosion
cycles.
Refineries have to assure amine and sulphur
plant performance and reliability in parallel
with production of low sulphur gasoline and
diesel. The Marsulex case study emphasizes
that there exists a robust and reliable means
to control particulate and liquid hydrocarbon
contamination.
Fuels and Chemicals
Visit us on the Web at www.pall.com
25 Harbor Park Drive
Port Washington, NY 11050
+1 516 484 3600
telephone
+1 888 873 7255
toll free US
Pall Corporation has offices and plants throughout the world. For Pall representatives
in your area, please go to www.pall.com/contact
Portsmouth - UK
+44 (0)23 9230 2357 telephone
+44 (0)23 9230 2509 fax
processuk@pall.com
Because of technological developments related to the products, systems, and/or
services described herein, the data and procedures are subject to change without
notice. Please consult your Pall representative or visit www.pall.com to verify that
this information remains valid. Products in this document may be covered by one
or more of the following patent numbers: EP 0 930 926; US 5,480,547; US
6,332,987; EP 0 667 800; EP 0 982 061; EP 1 380 331; US 5,543,047; US
5,690,765; US 5,725,784; US 6,113,784; US 7,083,564; US 7,318,800.
© Copyright 2009, 2011, Pall Corporation. Pall,
, PhaseSep, and Ultipleat are trademarks of
Pall Corporation. ® Indicates a trademark registered in the USA. Filtration. Separation. Solution.SM
is a service mark of Pall Corporation.
FCASRCSENa
Printed in the USA
July 2011